Method for preparing oxaziridines

ABSTRACT

THIS INVENTION RELATES TO A METHOD FOR PREPARING OXAZIRIDINES OF THE GENERAL FORMULA   2-R3,3-R1,3-R2-OXAZIRIDINE   WHEREIN R1 AND R2 EACH IS HYDROGEN ATOM, OR A NONSUBSTITUTED OR SUBSTITUTED LINER OF BRANCHED ALKYL OR CYCLOALKYL RADICAL HAVING A MAXIMUM OF 10 CARBON ATOMS. OR A NON-SUBSTITUTED OR SUBSTITUTED PHENYL RADICAL, SUBSTITUTION BEING WITH ONE OR MORE GROUPS WHICH ARE STABLE UNDER THE CONDITIONS OF THE REACTION WHEREBY SAID OXAZIRIDINES (I) ARE PRODUCED OR R1 AND R2 TOGETHER IS A LINEAR OR BRANCHED ALKYLENE RADICAL OF FROM 3 TO 11 CARBON ATOMS WHICH COMPRISES REACTING AN IMINE OF THE GENERAL FORMULA   R1-C(-R2)=N-R3   WITH HYDROGEN PEROXIDE AND A NITRILE OF THE GENERAL FORMULA   24-CN   WHEREIN R1 AND R2 HAVE THE AFORESAID MEANING AND R3 AND R4 EACH IS A NON-SUBSTITUTED OR SUBSTITUTED LINEAR OR BRACHED ALKYL OR CYCLOALKYL RADICAL HAVING A MAXIMUM OF 10 CARBON ATOMS OR A NON-SUBSTITUTED OR SUBSTITUTED PHENYL RADICAL, SUBSTITUTION BEING WITH ONE OR MORE GROUPS WHICH ARE STABLE UNDER THE CONDITIONS WHEREBY SAID OXAZIRIDINES (I) ARE PRODUCED AND RECOVERING SAID OXAZIRIDINES (i) FROM THE REACTION MEDIUM.

United States Patent U.S. Cl. 260-333 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method for preparing oxaziridines of the general formula wherein R and R each is a hydrogen atom, or a nonsubstituted or substituted linear or branched alkyl or cyoloalkyl radical having a maximum of 10 carbon atoms, or a non-substituted or substituted phenyl radical, substitution being with one or more groups which are stable under the conditions of the reaction whereby said oxaziridines (I) are produced or R and R together is a linear or branched alkylene radical of from 3 to 11 carbon atoms which comprises reacting an imine of the general formula C=NRa Rll (II) with hydrogen peroxide and a nitrile of the general formula R,CN

wherein R and R have the aforesaid meaning and R and R each is a non-substituted or substituted linear or branched alkyl or cycloalkyl radical having a maximum of 10 carbon atoms or a non-substituted or substituted phenyl radical, substitution being with one or more groups which are stable under the conditions whereby said oxaziridines (I) are produced and recovering said oxaziridines (I) from the reaction medium.

BACKGROUND OF THE INVENTION (I) Field of the invention This invention relates to a method for preparing oxaziridines of the general formula C NRa Br (I) which comprises reacting an imine of the general formula C=NRa with hydrogen peroxide and a nitrile R -CN 111 wherein R R R and R each has the above-designated meaning and recovering the oxaziridine (I) from the reaction medium.

(II) Description of the prior art The current methods for synthesizing oxaziridines require the use of uncommon, hence expensive, reactants or the use of relatively severe reaction conditions. For example, it has been proposed to epoxidate the correspond- 3,819,653 Patented June 25, 1974 SUMMARY OF THE INVENTION Applicants have discovered that oxaziridines of the general formula wherein R and R each is a hydrogen atom or a nonsubstituted or substituted linear or branched alkyl or cycloalkyl radical having a maximum of 10 carbon atoms, a non-substituted or substituted phenyl radical, substitution being with one or more groups which are stable under the conditions of the reaction whereby said oxaziridines (I) are produced or R and R together is a linear or branched alkylene radical of from 3 to 11 carbon atoms are conveniently prepared in good yields by reacting an imine of the general formula C=NRa R2 (II) with hydrogen peroxide and a nitrile of the general formula R4CN I wherein R and R have the aforesaid meaning and R and R each is a non-substituted or substituted linear or branched alkyl or cycloalkyl radical having a maximum of 10 carbon atoms or a non-substituted or substituted phenyl radical, substitution being with one or more groups which are stable under the conditions whereby said oxaziridines (I) are produced and recovering said oxaziridines (I) from the reaction medium.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Radicals R and R can be substituted with groups which are stable in the reaction medium whereby oxaziridines (I) are produced; examples of such stable groups include methyl, methoxy, chloro, bromo, fluoro and nitro groups. Other groups may be employed as is readily apparent to one skilled in the art.

It is advantageous to react the imine (H), hydrogen peroxide and nitrile (III) in aqueous medium or in the presence of an organic solvent inert with respect to the reaction components in order to facilitate homogenization of the reaction mixture.

Examples of solvents which may be employed in the process of this invention include the aliphatic monoalcohols having less than four carbon atoms which include methanol, ethanol, n-propanol, isopropanol, nbutanol, sec-butanol, isobutanol and tert-butanol.

It is advantageous to carry out the reaction at a temperature from about 0 C. to C. The reaction can be made to take place under atmospheric pressure, or if desired, at a pressure up to 10 atmospheres to maintain all the reactions in the liquid reaction medium.

The reactants can be used in equimolar quantity or one can use more of, or less then, one or another of the reactants. For example, from 0.2 to 5 moles imine (II) per mole of hydrogen peroxide can be reacted. The nitrile according to formula (III) is advantageously employed in a molar quantity which is equal to, or greater than, the hydrogen peroxide, for example, 1 to 10 moles nitrile (III) per mole of hydrogen peroxide.

It is advantageous to employ hydrogen peroxide as a 30-90% by weight aqueous solution such as supplied commercially.

It is advantageous to add one or more hydrogen per oxide stabilizing agents to the reaction medium or agents capable of buifering the pH of the reaction medium such as phosphoric acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, acetic acid or the alkaline metal or ammonium salts of such acids at a level of about 0.01 to 1.0% by weight of the reaction medium for each of these agents.

The oxaziridines (I) can be separated from the reaction medium using known and conventional methods, as for example, extraction with an immiscible solvent, fractional distillation or a combination of these two methods.

The oxaziridines (I) of this invention are useful as intermediates for the synthesis of lactams such as the N- substituted lactams, for example.

The following examples are illustrative of the process of this invention.

EXAMPLE 1 89.5 gm. (0.5 moles) cyclohexylidene cyclohexylamine, 20.5 gm. (0.5 moles) acetonitrile and 160 gm. methanol were charged into a reactor having a volume of 750 ml. The reaction mixture was heated to 40 C. and then over a period of 1 hour, 26.7 gm. of a 70% by weight aqueous solution of hydrogen peroxide (0.55 moles) were added. The medium was left to react for 3 hours and then methanol was removed therefrom under a pressure of 200 mm. Hg. 100 cm. water were then added to the residue and a first extraction with 100 cm. water was followed by two additional extractions each with 50 cm. chloroform. The organic layers were combined, washed with 50 cm. water and dried upon a bed of anhydrous N SO The chloroform was withdrawn under vacuum. Distillation of the residue provided 72 gm. (74% yield) of pentamethylene-N-cyclohexyloxaziridine (boiling point of 87 C.-88 C. at 0.2 mm. Hg) of the formula @TfQ identified by infra-red and mass spectrometry. The physical and spectral characteristics agree with those reported in the literature (cf. H. Krimm, Ben, 91, 1057 (1958)); the absorption band characteristic of the cyclic group being 1398 cmr EXAMPLE 2 30 gm. (0.236 moles) isobutylidene sec-butylamine, 75 gm. methanol, 27 gm. (0.236 moles) benzonitrile and 0.5 cm. 1.0 N NaOH were successively charged into a reactor. 12.6 gm. of 70% by weight (0.260 moles) hydrogen peroxide were then added drop by drop over a period of 30 minutes at ambient temperature (25 C.). After 3 hours and 30 minutes of reaction time, the methanol was evaporated, 50 ml. water were then added to the residue and extraction was carried out using 100 cm. chloroform. The organic layer was washed with 25 cm. water and dried upon a bed of anhydrous Na SO The chloroform was withdrawn by evaporation and upon distillation, 16.3 gm. (48.5% yield) isopropyl-N-sec butyloxaziridine (boiling point of 42 C. at 0.3 mm. Hg) of the formula 4. was recovered having an absorption band characteristic of the cyclic group of 1380 CHI-"1.

EXAMPLE 3 The procedure similar to that set forth in Example 2 was carried out except that benzonitrile was replaced by 9.6 gm. (0.236 moles) acetonitrile. Distillation under vacuum resulted in 16.2 gm. (48% yield) isopropyl-N- secbutyloxaziridine.

EXAMPLE 4 16.6 gm. of by weight aqueous of a solution (0.341 moles) of hydrogen peroxide were added drop by drop at ambient temperature to a mixture of 35 gm. (0.31 moles) isobutylidene isopropylarnine, 35.1 gm. (0.341 moles) benzonitrile, 99.2 gm. methanol and 0.6 cm. 1.0 N NaOI-I. After reacting for three hours, the methanol was evaporated, 50 cm. water were added to the residue and extraction was carried out using chloroform. The organic layer was washed with water, dried upon a bed of anhydrous Na SQ, and the solvent was removed by evaporation. The residue was subjected to vacuum distillation and 18.4 gm. of 2,3-diisopropyloxaziridine (also named isopropyl-N-isopropyloxaziridine) having a boiling point of 43 C.-45 C. at 1.2 mm. Hg and the formula were recovered. The compound has the absorption band characteristic of the cyclic group of 1370 cmr EXAMPLE 5 30.6 gm. (0.2 moles) isobutylidene cyclohexylamine, 20.6 gm. benzonitrile (0.2 moles) and 64 gm. methanol were successively charged into a reactor having a volume of 250 cm. The reaction medium was heated to 40 C. and then, over a period of 30 minutes, 9.7 gm. (0.2 moles) of a 70% by weight aqueous solution of hydrogen peroxide was added. After reacting for five hours, the methanol was removed under vacuum and the residue was subjected to extraction with chloroform. The organic phase was washed with water and dried upon a bed of anhydrous Na SO After withdrawal of the solvent, 17.2 gm. of 2-cyclohexyl-3-isopropyloxaziridine (having a boiling point of 42 C. at 0.2 mm. Hg) and an absorption band characteristic of the cyclic group at 1370 cm. were recovered.

We claim:

1. A method for preparing oxaziridines of the general formula:

wherein R and R each is a hydrogen atom, a nonsubstituted C C alkyl, or non-substituted cycloalkyl radical having a maximum of 10 carbon atoms, or a non-subsittuted phenyl radical, or a substituted C C alkyl, or a substituted cycloalkyl having a maximum of 10 carbon atoms, or a substituted phenyl radical, said substitution being with one or more groups which are stable under the conditions of the reaction whereby said oxaziridines (I) are produced, or R and R together is an al kylene radical of from 3 to 11 carbon atoms which comprises reacting an imine of the general formula wherein R and R have the aforesaid meaning and R and R each is a non-substituted C -C alkyl or a nonsubstituted cyeloalliyl radical having a maximum of 10 carbon atoms or anon-substituted phenyl radical, or a substituted C -C .alkyl or a substituted c'ycloal kyl hav- 5. The method of claim 1 wherein the reaction temperature is in the range from about 0 C. to 100 C.

6. The method of claim 1 wherein the reaction pressure is less than, the same as or up to about 10 times greater than atmospheric pressure.

7. The process of claim 1 wherein imine (II), hydrogen peroxide and nitrile (III) are present in approximately equimolar amounts.

8. The process of claim 1 wherein from about 0.2 to moles imiine (II) per mole of hydrogen peroxide are reacted.

9. The process of claim 1 wherein from about 1 to moles nitrile (IH) per mole of hydrogen peroxide are reacted.

ing 'a maximum of 10 carbon atoms or a substituted phenyl said substitution being with 1 or more groups which are stable under the conditions whereby said oxaziridines (I) are produced and recovering said oxaziri- Emmons, W. D.: The Preparation and Properties of Oxiziranes, J. Chem. Soc., 1957, pp. 5739-54.

HENRY R. JILES, Primary Examiner M. A. M. CROWDER, Assistant Examiner UNITED STATES ?ATENT OFFICE CERTIFICATE @F QU REUHQN atent N 3,819,653 Dated June 25 1974 Inventor(5) Jean-Pierre Schirmann and Francis Weiss It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

R 1. In column 1, line 30, should read C N"R3 R 5 n H R 2. In column 1,. line 57, 7 should read C=N-R 3 Rx R =N-R 3. In-column 2, line 68, "all the reactions" should read all "the reactants 4. In column 5 line 5 l should read C N R3 R R l 3 U C-N R s. In c zolunm 5, line 12, "R a dR should read --R 'lnd R Signed aha seared "ram-29m M October 1914?" (SEAL) Attest:

McCOY M. GIBSON JR. (2. MARSHALL DANN- Attesting Qfficer Commissioner of Patents FORM PC4050 (10459) 7 uscoMM-oc scan-Pas 3* U.S. GOVERNMENT PRINTING OFFICE- 1989 0-356-334, 

